In humans, injury or noxious sensations result in both a sensory and emotional response, which together create the subjective experience of pain. You can learn more about how human brains produce the experience of pain by watching this TED-Ed lesson: How does your brain respond to pain? Being able to avoid experiencing pain is important to us. A great deal of research has been done on how to relieve pain in humans and in other vertebrate animals, and we now have a very good understanding of how pain works in health and disease. These TED Ed lessons address chronic pain: The mystery of chronic pain and How do pain relievers work?

However, we still know very little about how animals that are unlike us might experience pain. Animals such octopuses, lobsters, and insects have very complex nervous systems, although they differ in fundamental ways from our own. A complex brain is considered an essential requirement for being capable of experiencing pain, but in general we know little about how invertebrate animals like insects, molluscs and crustaceans might respond to potentially painful stimuli. Scientists are working to understand these questions so that we can develop ways to treat pain in animals whose nervous system anatomy, pharmacology and physiology differ drastically from our own.

Nociception has been described in many invertebrate animals, so the question is not whether they can respond reflexively to noxious sensation, but whether they are also capable of the emotional response to injury that defines pain in humans and other mammals. This is a controversial question that has broad ramifications for agriculture, commercial fishing, the pet trade, and for scientific research that uses invertebrate animals’ nervous systems to learn about our own. This article will provide some background: Do invertebrates feel pain?

In some countries, government agencies have decided that there is enough evidence to conclude that some invertebrate animals do experience pain in the same way as vertebrate animals, but there is still a lack of scientific evidence to support this conclusion. And we also lack a good set of measures to let us determine if an animal like a shrimp or an octopus is feeling pain. This makes it hard to know, for example, whether a drug we give is effective at relieving pain.

Although it seems obvious that we should avoid causing pain to animals, it is much more complicated to know how we can best achieve this. Given that we continue to use animals, both vertebrates and invertebrates, in many ways (some of which may indeed by painful), researchers are focusing on learning how best to measure, reduce and alleviate pain. Our ultimate goal is to prevent pain, in all the animals we interact with.

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